Conventionally, there is known a power source control network in which a master logical device and a slave logical device are connected to each other (for example, see Japanese Laid-open Patent Publication No. 62-500269). On the network, all of communication is performed between the master logical device and the slave logical device.
There is known a technology in which a client device having a power source control device is connected to a LAN (Local Area Network) together with a host computer (for example, see Japanese Laid-open Patent Publication No. 6-112960). Moreover, there is known a technology in which one of servers that are connected to an uninterruptible power source via communication cables is determined as a master server, the others are determined as slave servers, and a shut-down instruction is sent to the slave servers when the master server detects a power source abnormity of the uninterruptible power source (for example, see Japanese Laid-open Patent Publication No. 2005-78174).